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Source control policies
We essentially follow this git branching model. Developers are expected to use the full model locally, the main MathJax repository should primarily contain develop, master and release branches (both core and for mathjax-node) as well as branches with open PRs (possibly marked WIP).
We are using git via GitHub as the main source control mechanism for MathJax; the SVN repository at Sourceforge has been discontinued in 2011.
- We need a develop branch for active development. While we will attempt to keep the develop stable, it will change rapidly as development proceeds. It follows no users should use the develop branch for production purposes.
- We need stable release branches that are always guaranteed to point to a stable, tested version. These are branches that users can use for production.
- We need to be able to make Hotfixes for bugs to releases and deploy them as "point releases" between major releases.
- We need to be able to use source control to share "candidate release" files for testing before releasing them as major or hotfix releases.
- We need to periodically package release snapshots for distribution (e.g. zip files) and be able to restore via source control to the code state corresponding to any given snapshot.
Note that the requirements basically identify two roles for source control.
- It serves the needs of the development process by allowing developers to work independently, merge work together, and maintain a history of code state.
- It seves as a distribution mechanism for obtaining released software and Hotfixes.
Many projects use only a single master code line and don't maintain release branches. The reason we want to do this is that we anticipate users who will need hotfixes (e.g. for bugs introduced by browser updates) but that won't want to update to the master development line. For example, if a user has customizations that would need updates due to changes in the master line unrelated to the hotfix, they may not have time and resources to do that work just to get the hotfix.
The following is quoted from http://nvie.com/posts/a-successful-git-branching-model/, Published: January 05, 2010
The repository setup that we use and that works well with this branching model, is that with a central “truth” repo, https://github.com/mathjax/MathJax/.
Each developer pulls and pushes to origin. But besides the centralized
push-pull relationships, each developer may also pull changes from other
peers to form sub teams. For example, this might be useful to work
together with two or more developers on a big new feature, before
pushing the work in progress to origin prematurely. .
The central repo holds two main branches with an infinite lifetime:
masterdevelop
The master branch at origin should be familiar to every Git user.
Parallel to the master branch, another branch exists called develop.
We consider origin/master to be the main branch where the source code
of HEAD always reflects a production-ready state.
We consider origin/develop to be the main branch where the source code
of HEAD always reflects a state with the latest delivered development
changes for the next release. Some would call this the “integration
branch”. This is where any automatic nightly builds are built from.
When the source code in the develop branch reaches a stable point and
is ready to be released, all of the changes should be merged back into
master somehow and then tagged with a release number. How this is done
in detail will be discussed further on.
Therefore, each time when changes are merged back into master, this is
a new production release by definition. We tend to be very strict at
this, so that theoretically, we could use a Git hook script to
automatically build and roll-out our software to production servers
every time there was a commit on master.
Next to the main branches master and develop, our development model
uses a variety of supporting branches to aid parallel development
between team members, ease tracking of features, prepare for production
releases and to assist in quickly fixing live production problems.
Unlike the main branches, these branches always have a limited life
time, since they will be removed eventually.
The different types of branches we may use are:
- Feature branches
- Release branches
- Hotfix branches
Each of these branches have a specific purpose and are bound to strict rules as to which branches may be their originating branch and which branches must be their merge targets. We will walk through them in a minute.
By no means are these branches “special” from a technical perspective. The branch types are categorized by how we use them. They are of course plain old Git branches.
May branch off from: develop
Must merge back into: develop
Branch naming convention: anything except master, develop,
release-*, or hotfix-*
Feature branches (or sometimes called topic branches) are used to
develop new features for the upcoming or a distant future release. When
starting development of a feature, the target release in which this
feature will be incorporated may well be unknown at that point. The
essence of a feature branch is that it exists as long as the feature is
in development, but will eventually be merged back into develop (to
definitely add the new feature to the upcoming release) or discarded (in
case of a disappointing experiment).
Feature branches typically exist in developer repos only, not in
origin.
When starting work on a new feature, branch off from the develop
branch.
$ git checkout -b myfeature develop
Switched to a new branch "myfeature"
Finished features may be merged into the develop branch definitely add
them to the upcoming release:
$ git checkout develop
Switched to branch 'develop'
$ git merge --no-ff myfeature
Updating ea1b82a..05e9557
(Summary of changes)
$ git branch -d myfeature
Deleted branch myfeature (was 05e9557).
$ git push origin develop
The --no-ff flag causes the merge to always create a new commit
object, even if the merge could be performed with a fast-forward. This
avoids losing information about the historical existence of a feature
branch and groups together all commits that together added the feature.
May branch off from: develop
Must merge back into: develop and master
Branch naming convention: release-*
Release branches support preparation of a new production release. They
allow for last-minute dotting of i’s and crossing t’s. Furthermore, they
allow for minor bug fixes and preparing meta-data for a release (version
number, build dates, etc.). By doing all of this work on a release
branch, the develop branch is cleared to receive features for the next
big release.
The key moment to branch off a new release branch from develop is when
develop (almost) reflects the desired state of the new release. At least
all features that are targeted for the release-to-be-built must be
merged in to develop at this point in time. All features targeted at
future releases may not — they must wait until after the release branch is
branched off.
Release branches are created from the develop branch. For example, say
version 1.1.5 is the current production release and we have a big
release coming up. The state of develop is ready for the “next
release” and we have decided that this will become version 1.2 (rather
than 1.1.6 or 2.0). So we branch off and give the release branch a name
reflecting the new version number:
$ git checkout -b release-1.2 develop
Switched to a new branch "release-1.2"
$ ./bump-version.sh 1.2
Files modified successfully, version bumped to 1.2.
$ git commit -a -m "Bumped version number to 1.2"
[release-1.2 74d9424] Bumped version number to 1.2
1 files changed, 1 insertions(+), 1 deletions(-)
After creating a new branch and switching to it, we bump the version
number. Here, bump-version.sh is a fictional shell script that changes
some files in the working copy to reflect the new version. (This can of
course be a manual change — the point being that some files change.)
Then, the bumped version number is committed.
This new branch may exist there for a while, until the release may be
rolled out definitely. During that time, bug fixes may be applied in
this branch (rather than on the develop branch). Adding large new
features here is strictly prohibited. They must be merged into
develop, and therefore, wait for the next big release.
When the state of the release branch is ready to become a real release,
some actions need to be carried out. First, the release branch is merged
into master (since every commit on master is a new release by
definition, remember). Next, that commit on master must be tagged for
easy future reference to this historical version. Finally, the changes
made on the release branch need to be merged back into develop, so
that future releases also contain these bug fixes.
The first two steps in Git:
$ git checkout master
Switched to branch 'master'
$ git merge --no-ff release-1.2
Merge made by recursive.
(Summary of changes)
$ git tag -a 1.2
The release is now done, and tagged for future reference.
Edit: You might as well want to use the -s or -u <key> flags to
sign your tag cryptographically.
To keep the changes made in the release branch, we need to merge those
back into develop, though. In Git:
$ git checkout develop
Switched to branch 'develop'
$ git merge --no-ff release-1.2
Merge made by recursive.
(Summary of changes)
This step may well lead to a merge conflict (probably even, since we have changed the version number). If so, fix it and commit.
Now we are really done and the release branch may be removed, since we don’t need it anymore:
$ git branch -d release-1.2
Deleted branch release-1.2 (was ff452fe).
May branch off from: master
Must merge back into: develop and master
Branch naming convention: hotfix-*
Hotfix branches are very much like release branches in that they are also meant to prepare for a new production release, albeit unplanned. They arise from the necessity to act immediately upon an undesired state of a live production version. When a critical bug in a production version must be resolved immediately, a hotfix branch may be branched off from the corresponding tag on the master branch that marks the production version.
The essence is that work of team members (on the develop branch) can
continue, while another person is preparing a quick production fix.
Hotfix branches are created from the master branch. For example, say
version 1.2 is the current production release running live and causing
troubles due to a severe bug. But changes on develop are yet unstable.
We may then branch off a hotfix branch and start fixing the problem:
$ git checkout -b hotfix-1.2.1 master
Switched to a new branch "hotfix-1.2.1"
$ ./bump-version.sh 1.2.1
Files modified successfully, version bumped to 1.2.1.
$ git commit -a -m "Bumped version number to 1.2.1"
[hotfix-1.2.1 41e61bb] Bumped version number to 1.2.1
1 files changed, 1 insertions(+), 1 deletions(-)
Don’t forget to bump the version number after branching off!
Then, fix the bug and commit the fix in one or more separate commits.
$ git commit -m "Fixed severe production problem"
[hotfix-1.2.1 abbe5d6] Fixed severe production problem
5 files changed, 32 insertions(+), 17 deletions(-)
Finishing a hotfix branch
When finished, the bugfix needs to be merged back into master, but
also needs to be merged back into develop, in order to safeguard that
the bugfix is included in the next release as well. This is completely
similar to how release branches are finished.
First, update master and tag the release.
$ git checkout master
Switched to branch 'master'
$ git merge --no-ff hotfix-1.2.1
Merge made by recursive.
(Summary of changes)
$ git tag -a 1.2.1
Edit: You might as well want to use the -s or -u <key> flags to
sign your tag cryptographically.
Next, include the bugfix in develop, too:
$ git checkout develop
Switched to branch 'develop'
$ git merge --no-ff hotfix-1.2.1
Merge made by recursive.
(Summary of changes)
The one exception to the rule here is that, when a release branch
currently exists, the hotfix changes need to be merged into that release
branch, instead of develop. Back-merging the bugfix into the release
branch will eventually result in the bugfix being merged into develop
too, when the release branch is finished. (If work in develop
immediately requires this bugfix and cannot wait for the release branch
to be finished, you may safely merge the bugfix into develop now
already as well.)
Finally, remove the temporary branch:
$ git branch -d hotfix-1.2.1
Deleted branch hotfix-1.2.1 (was abbe5d6).